Self-Assembly of Trioxyethylene-Encapsulated Gold Nanoclusters under Aqueous Conditions

The aqueous self-assembly of methyl-terminated tri(oxyethylene)thiol-encapsulated gold nanoclusters of varying core size is demonstrated on micrometer scale Au/SiO<INF>2</INF> interdigital electrodes. This self-assembly process consists of alternate exposures of the substrate to solutions of either an α,ω-dithiol or the gold nanoclusters, resulting in the deposition of these materials onto the electrode surface. A comparison of the procedure in both H<INF>2</INF>O and CHCl<INF>3</INF> solvents shows that the assembly, as monitored by the electrical conductivity of the device, occurs more rapidly in the H<INF>2</INF>O system. This observation is complimented by XPS and UV/Vis measurements, which show that (1) the increased current is due to an increased amount of gold deposited on the surface under aqueous conditions and (2) the thiol exchange reaction occurs more rapidly in H<INF>2</INF>O in comparison to CHCl<INF>3</INF>.